2D Carbide MXene under postetch low-temperature annealing for high-performance supercapacitor electrode

MXene, as an emerging class of conductive two-dimensional materials, have extraordinary applications in the field of electrochemical energy storage. However, the intrisic capacity of MXene still need to be improved due to the large gap to their theoretical capacity. Here, we provide a facile and new strategy to enhance their electrochemical performance-postetch low-temperature annealing (below 400 degrees C) under Ar atmosphere. Due to the formation of more C-Ti-O active sites and larger interlayer voids, the Ti3C2Tx freestanding film annealed under 200 degrees C exhibits a high capacitance of 429 F/g and energy density of 29.2 Wh/Kg in 1 M H2SO4 electrolyte, it could withstand 5000 cycles with 89% of the capacitance retention. By comparison, the Ti3C2Tx annealed at higher temperature (400 degrees C), presented a high resistance and poor electrochemical property because of partial oxidation and breaking of Ti-C bond on the surface of MXene nanosheets, despite the larger interlayer voids and low -F contents, . This work is not only probing the importance to maintain the original structure of MXene but also proposing a new strategy to realizing a high capacitance of pure MXene electrode. (C) 2020 Elsevier Ltd. All rights reserved.